Engine detonation control by acoustic methods and apparatus



A. G. BOBINE, JR ENGINE OETONATION CONTROL BT ACOUSTIC Aug. 28, 1956 METHODS AND APPARATUS Filed oct 12 195s INVENTOR. MBE/P7' G500/NL. JR

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United .States Patent() YENGINE DETONATION CONTROL B Y ACOUSTIC NIETHODS AND APPARATUS Albert G. Bodine, Jr., Van Nuys, Caiif.

Application October 12, 1953, Serial No. 385,479

12 Claims. (Cl. y123-191) This invention relates generally to internal combustion engines and to means for suppressing irregular burning and detonation of fuel-air mixtures in internal combustion engines. The presentapplication is directed to improvements in the eld covered by my Patent No. 2,573,536, issued October 30, 1951, and entitled Engine Detonation Control by Acoustic Methods and Apparatus. For a full disclosure of the acoustic aspects of detonation in combustion, and my basic solution for controlling detonation in combustion, reference should be had to my said Patent No. 2,573,536. The present application is a continuation-in-part of my prior application Ser. No. 24,744, led May 3, 1948, for Acoustic Means for Suppressing Detonation in Internal Combustion Engines.

The present invention is based on the now known fact that detonation in an engine combustion chamber produces sound waves, a large part of which rise to high amplitude at resonant lfrequencies of the chamber, and on my discovery that these sound waves help produce the various well known and harmful manifestations of detonation. According to my basic invention, l reduce or eliminate these harmful effects by attenuating the high amplitude detonation-induced sound waves, and this is done by use in connection with the combustion chamber of acoustic attenuation means made responsive to the frequencies at which the detonation-induced sound waves tend to appear at high amplitudes.

A general object of the present invention is the provision of an improved and advantageous acoustic attenuator combined with the combustion chamber of an internal combustion engine.

A further object is the provision of an improved acoustic attenuator for an internal combustion engine, characterized by ,being positioned within the chamber in a Yunique and highly vadvantageous position for reaching the pressure antinode regions of various Vstanding sound wave patterns encountered in a combustion chamber of an internal combustion engine.

In my above mentioned parent application Ser. No. 24,744, there was disclosed a form of Vdetonation-suppressor comprising a thick .gasket vor .pad 39 of porous material, composed typically of sintered, .powdered metal, used between the engine block and head, its `inner periphery being exposed to or forming a yportion ofthe combustion chamber at the juncture of engine block andcylinder head. This subject matter is repeated and claimed herein. This porous pad or b odyprovides .a sound wave attenuator in the nature of an absorber body. An absorber body is ,known to have a degree o f resonant o r best response to a particular sound wave frequency or frequency range,

'though of course the degree of selectivity is nowhere ,near

as marked as with highly resonant or high Q devices such as Helmholtz resonators or quarter-wave pipes, for example. Preferably, this characteristic Vis taken advantage of, and lthe porous body designed, in accordance with sknown acoustic principles, to have its effective re- .freqneneygrange Lto be combatted.

In `my aforementioned Patent No. 2,573,536 I described the vtypical resonant standing wave patterns easily ascertainable in a combustion chamber of an internal combustion engine see Figs. l to 4 of said patent), and the -fact lthat such resonant standing Wave patterns can best be combatted by attacking them at their pressure antinode regions was discussed, From this disclosure in my said prior patent, it may be understood that pressure antinode regions of the characteristic standing wave patterns commonly found in a combustion chamber of an engine are located about the periphery of the chamber. With this in mind, it may be seen that the sound wave absorber of the present invention, extending as it does about the periphery of the combustion chamber, is in a most advantageous position for absorbing sound wave energy from the pressure antinode regions of the standing waves which tend to be set up in the chamber. Actually, substantial results are obtainable by means of a Wave absorber extending only part way around the chamber, as for instance, through an arc of Such limited extension of the absorber is suicient to assure overlapping of at least one of the pressure antinode regions of the several patterns normally encountered, and is sufiicient to assure substantial attenuation of the entire standing wave system. It is accordingly within the scope of the present invention. However, while it is true that it is not essential for the absorber to extend around the full 360 of the chamber, and a substantial coverage, such as 90, will assure substantial wave attenuation, it is of distinct advantage and a further improvement to provide an absorber which entirely encircles the chamber, this overall coverage positively assuring the maximum of attenuation and removing any possibility of missing any mode so long as it has one pressure antinode in the peripheral region of the chamber.

The absorber of the invention, porous, or of other types, as will be described, mounted between the cylinder head and block, has a further advantage, not possessed -by many other-forms of my attenuators, in that its outer periphery is exposed to outside atmosphere and can hence radiate heat and therefore operate at a cooler temperature than thel gas in the combustion chamber. Furthermore, it has considerable area in heat transfer relationship with the engine cooling system. By thus operating at -a reduced temperature, the speed of sound through the porous structure is reduced, and attenuation improved.

rlfhe invention will be better understood from the following detailed description of an engine equipped with a preferred form thereof, reference Vfor this purpose being had yto the accompanying drawings, in which:

lFig. l is a transverse .section through an engine block and cylinder head embodying one illustrative form of the invention;

'P ig. 2 Yis a fragmentary view showing a modication; and

Fig. 3 is a fragmentary view showing a second modication.

In lthe drawings, numeral 10 designates generally a water-cooled engine block for a valve-in-head internal combustion engine, and numeral 11 designates the watereooled vhead of the engine. vBetween the block and head is a sound wave absorber pad 12 of porous substance, typically composed of `sintered, powdered metal, porous bronze, or other heat-resistant material of porous composition. Gaskets 1,3 and 14 are used between the opposed plane faces .on the block and pad, and on the pad and head, respectively. This absorber body or pad will be understood to have minute tubes or passageways of capillary dimensions, extending tortuously through it. These tubes or passageways comprise intercommunicating pores, cells or crevices, and the passageways formed therebyaretortuous in character and irregular in direc- 3 tion. The result is a structure into which the sound waves are received and throughout which the waves are attenuated and extinguished by frictional scrubbing of the gas molecules on one another'within the Vcapillarylike passages, the sound wave energy being `dissipated as heat.

Further describing the typical engine structure, the block lil is formed with cylinder receiving reciprocating piston 16; and the head 11 and bore surface 12a in porous pad l2 define a combustion chamber 17 over cylinder l5 and piston 16. Further illustrated are conventional rocker-operated valves 18 and 19, and a spark plug 2t) located at the top of the combustion chamber.

ln operation, a detonation pressure wave initiated within the combustion chamber of the engine, above the piston, sets up resonant sound waves within the combustion chamber at natural resonant frequencies of the latter.

These sound waves may form standing wave patterns,

with pressure antinodes in the peripheral regions of the combustion chamber, as described in my Patent No. 2,573,536. The pressure waves thus set up in the combustion chamber, particularly in the peripheral regions of the chamber where the pressure antinode regions tend to occur, encounter the inner peripheral surface 12a of the porous absorber 12, and are absorbed and attenuated in accordance with principles set forth in my aforesaid patent. As earlier stated, a porous sound wave absorber generally has a frequency response to a particular frequency range, and it is preferred that the absorber be designed, in accordance with known acoustic technique, to be responsive to the particular sound wave frequencies or frequency ranges ascertainable in the particular combustion chamber to which the invention is being applied. ln the practice of the invention, therefore, the frequencies at which resonant peaking of sound waves tend to occur can be readily ascertained by known acoustic technique, and the absorber body 12 then designed so that the sound wave frequencies of the engine which are to be attenuated come within the principal response range of the absorber.

lt will be seen that the absorber body as thus described has the prime advantage that it is inherently close coupled to the peripheral high impedance or pressure antinode regions of resonant standing sound wave patterns commonly set up in the combustion chamber of an internal combustion engine. With the intimate relation thus established between absorber body and pressure antinode regions of the offensive wave patterns, maximum destruction of the offensive wave patterns is assured.

En 2 has been shown a modified absorber 22 understood to encircle a combustion chamber space over the cylinder, being accommodated in an annular notch or pocket 23 formed in a bored insert plate 39a which replaces the porous body l2 of the embodiment of Fig. l. ri`he absorber 22 consists of a thin, hollow metallic O-ring 24, pre-loaded with highly co-mpressed gas, and preferably iilled with a highly sound wave attenuative material such as fiberglass, as indicated at 25. The thin shell 24 is preferably initially of circular cross-section, and of somewhat greater cross-section than the width dimension of the pocket into which it is installed. Accordingly, at time of installation of the cylinder head, the shell 24 is somewhat mashed down and attened to take the shape shown in Fig. 2. The gas pressure inside the tube 24 keeps it from collapsing under cylinder pressure. It will be seen that this form of absorber is also placed in the peripheral region of the combustion chamber, in intimate, close coupled relationship to the high impedance or pressure antinode regions of the common Wave patterns set up in such a chamber. It is also possible and preferable that the absorber 22 be designed for best response to the detonation sound wave frequencies encounteredin the combustion chamber. in operation, the pressure waves at the periphery of the combustion chamber encounter the thin shell 24 of the absorber 22 and are transmitted therethrough into the highly attenuative fiberglass body 25. It will be seen that the thin tube 24 acts, in effect, as a thin vibratory diaphragm, capable of transmitting the wave to the attenuative substance 25 contained Within it. Instead of a pressurized gas contained inside the tube 24, l may use a suitable liquid, preferably one of low acoustic impedance characteristic, i. e., one capable of coupling to the compressed combustion chamber gases in vibratory energy transmitting relationship.

Fig. 3 shows still another modification, where the absorber, again understood to encircle a peripheral region of the combustion chamber, comprises a low impedance semi-solid substance like silicon rubber, having the capability for sound wave absorption and dissipation, and at the same time high heat resistant properties. Such an absorber body is indicated at 40, of approximately triangular cross-section, with its base exposed to the combustion chamber. This body 40 is confined in a triangular pocket 41 formed between an insert annulus 39b, substituted for the porous body 25 of Fig. 2, and the adjacent face of the cylinder head. The equivalent of the thin metal tube or shell 24 of Fig. 2 is provided in the case of Fig. 3 by giving the body 40 a thin protective metal shell 42 by means of electroplating.

It will be seen that the various disclosed forms of absorbers are uniquely and advantageously placed to define a lower region of the combustion chamber, so as not to interfere with its conventional shape in the head, but so as to extend around it and form a lower extension thereof. So located, the absorber is in the most advantageous position possible for destruction of the pressure antinode regions of the wave patterns of a combustion chamber.

The drawings and description show certain present illustrative embodiments of the invention, but it is to be understood that these are illustrative only, and that the invention may take various other forms without departing from its spirit and scope.

I claim: n

l. In an internal ycombustion engine, the combination of: an engine block formed with a cylinder, a cylinder head having a combustion chamber space over said block, and an annular member interposed between said block and cylinder head including an arcuate sound Wave absorber extending for a substantial distance around the circle dened by the upper end of said cylinder and having an attenuative response for detonation wave frequencies occurring within the combustion chamber.

2. The subject matter of claim l, wherein said absorber extends at least approximately degrees around the circle defined by the upper end of the cylinder.

3. The subject matter of claim l, wherein said absorber extends entirely around the circle dened by the upper end of the cylinder.

4. The subject matter of claim l, wherein said absorber comprises a porous body.

5. The subject matter of claim 3, wherein said absorber comprises a porous body.

6. The subject matter of claim 3, wherein said absorber comprises a thin elastic tube filled with uid under pressure, and sound wave attenuative material packed inside said tube.

7. The subject matter of claim 3, wherein said absorber comprises a heat resistant metal coated rubberlike annulus.

8. In an internal combustion engine, the combination of: an engine block formed with a cylinder and having an upper face, a sound wave absorber pad having a lower face mounted on said block face and formed with a bore adjoining saidcylinder, said pad having an upper face, and a cylinder head having a lower face mounted on'said upper face of said pad, said cylinder head and said bore in said pad forming a combustion chamber over said cylinder, said absorber pad having an attenuative re,-

sponse to detonation sound wave frequencies occurring in said combustion chamber.

9. The subject matter of claim 8, wherein said absorber pad comprises a porous body.

10. In an internal combustion engine, the combination of: an engine block formed with a cylinder and having an upper face, an insert plate having a lower face mounted on said block face and formed with a bore adjoining said cylinder, said plate having an upper face, a cylinderhead having a lower face mounted on said upper face of said plate and formed to provide combustion chamber space above the bore in said plate, an internal circumferential pocket sunk in the bore surface of said plate, and a sound wave attenuator ring lodged in said pocket and having an attenuative response for detonation wave frequencies.

tenuator ring comprises a heat resistant metal coated rubber-like body.

References Cited in the tile of this patent UNITED STATES PATENTS 1,835,971 Schattanek Dec. 8, 1931 2,573,536 Bodine Oct. 30, 1951 

